This invention relates to a multiple head positioning apparatus for woodworking machines and the like.
As more fully disclosed in the present inventor's issued U.S. Pat. No. 4,874,996, woodworking apparatus includes a computer base control unit for the absolute positioning of the multiple tool units which are located and form a part of woodworking apparatus. Woodworking machines are typically high production machinery which include a plurality of different working tools mounted on longitudinally spaced stations. Each tool requires a multiplicity of axes for accurate positioning in accordance with various programmed cuts to be executed on wood members or parts passing through the machine. The cost of the machinery is related to the number of different stations incorporated into the apparatus and, significantly, by the positioning controls for effecting precise positioning of the many tools in space. The above patent is particularly directed to a computer based control unit for absolute positioning control in a relatively rapid and effective manner. Thus for example, the tool units in a relatively large machine are positioned within a time frame of three to eight minutes using the teaching of that patent. Generally that patent discloses a main CPU processor for controlling of the machine. A multiplex receiver board is provided for sequentially positioning of the various tools via a plurality of relay boards. The system includes a capacitive based sensor providing an absolute position control for each axes of the tool positioning apparatus. Each axes is positioned with a high speed movement till it reaches a selected position after which the head is moved in a final slow motion to establish a relatively accurate position. High speed positioning may use a rapid open loop control with all heads moving simultaneously to a rough position. Thereafter, a slow speed motion is established with a closed loop control system, with the tools being sequentially moved to a final position. The slow speed and sequential setting established accurate positioning. As applied to a 50 axes machine, tools may be located in a time frame of three to eight minutes. Other advantageous uses of that system are disclosed.
However, as also disclosed in that patent, there is a continuing need, almost consistently arising, in this type of machinery to further increase the efficiency of the machinery as a result of the unusually high cost associated with multiple head devices. Although three to eight minutes was a significant advance at the time of the prior invention, there is a continuing need to further reduce the setup time, as well as to improve the reliability and to reduce the maintenance and processing of the equipment.